The present invention is directed to what are commonly referred to as chip cards. A chip card is a credit card sized card in which a semiconductor device (referred to as an electronic "chip") is included for data storage and/or processing.
More specifically, the invention is directed to a chip card wherein the energy supply and bidirectional data exchange are effected via contacts on the card.
A contacting chip card of the type to which the invention relates, also referred to as a portable storage medium, is described in German patent application DE 3721170 having corresponding U.S. Pat. No. 4,874,934, the teachings of which are fully incorporated herein by reference. It is set forth in the abstract of U.S. Pat. No. 4,874,934 that the card includes an integrated circuit memory for storing predetermined information which also is embossed on the surface of the card, and a central processing unit. When a read instruction is supplied from a portable memory medium handling system externally connected to a portable memory medium, the central processing unit reads out the predetermined information stored in the memory, and supplies it to the portable memory medium handling system, which then displays the information on a display unit. An operator compares the information displayed on the display unit with the information embossed on the portable memory medium, and thus determines the authenticity of the embossed information. The disclosed card can serve as a credit card for purchasing purposes.
In German Patent 3721822, the teachings of which are fully incorporated herein, there is disclosed a contact-free chip card including an integrated circuit which is accessed by a reader coupled to a terminal and which receives electrical energy via an inductive coupling. The card is made of an insulating material into which the integrated circuit is embedded on a carrier. At the center of the circuit, a digital processor is mounted. An antenna coil provided for transmission is wound concentrically around the active surface of the integrated circuit semiconductor body.
There exists an international ISO Standard 7816 for chip cards that have contacts for bidirectional data transmission. Both contact utilizing and contact-free chip cards are available in the marketplace. Contact utilizing chip cards usually conform to International ISO Standard 7816 for transmission of power and data. Data flow, data formats, and clock frequencies are also proposed for standardization for contact-free chip cards so that occupation of the contact field of such cards of different write/read modules is the same.
As with the card described in DE 3721822 C1, the transmission of power and data for a contact-free chip card usually is accomplished using general transformer principles. Transmission makes use of the properties of electromagnetic waves at various frequency ranges.
Commercially available contacting chip cards are currently subjected to increasing competition from contact-free chip cards due to the disadvantages of the use of contacts: wear, contact resistances, requirement of direct connections to the electronics, static charging via the contacts, and design limitations imposed by contact positioning, among others.